Over 1,000,000 non-melanoma skin cancers are diagnosed annually in the US, making these the most common type of cancer and the fifth most costly cancer type in the Medicare population. Approximately eighty percent of nonmelanoma skin cancers are basal-cell carcinomas, and twenty percent are squamous-cell carcinomas (SCC). Unlike almost all basal-cell carcinomas, cutaneous squamous-cell carcinomas are associated with a substantial risk of metastasis. The principal precursor of cutaneous squamous-cell carcinoma is actinic keratosis (AK). AK has been described as a type of carcinoma in situ or SCCIS, in which carcinoma involves only the epidermis. Some of AK may evolve into invasive squamous-cell carcinoma. Options for treating AK include cryosurgery, electrodesiccation and curettage, topical fluorouracil, dermabrasion, and laser resurfacing.
On histological examination actinic keratoses and invasive squamous-cell carcinomas exhibit a spectrum of neoplastic changes. From a therapeutic standpoint, it is impractical and unnecessary to treat each individual keratotic lesion. Only patients with many lesions are followed closely, and thus, many events or tumor progression are undetected until at an advanced stage. Therefore, accurate prognostic markers and targeted therapies as well as more effective early chemopreventive strategies are necessary so that evolving squamous-cell carcinomas can be detected and treated expeditiously.